1. Field of the Invention
The present invention generally relates to audio/video systems and, more particularly, to simultaneous display of multiple audio/video programs transmitted over a digital link.
2. Description of the Related Art
Recently, high definition televisions (HDTVs) with digital interfaces, such as an IEEE 1394 bus interface, have appeared on the market. The IEEE 1394 bus (also referred to as FireWire, iLink, or DTV-Link) is a high-speed serial bus for transmitting digital data. In a typical configuration, a user employs an external tuning device, such as a set-top box (STB), to receive audio/video (AV) signals from a cable or satellite operator, or from a terrestrial broadcast. The STB, or “source device”, tunes to a particular AV signal to receive an AV stream, which is coupled to the digital bus. For example, the AV stream may include compressed AV data in accordance with the MPEG (Moving Pictures Expert Group) standard and the source device may output an MPEG-2 transport stream to the digital bus. The HDTV, or “sink device”, receives the AV stream over the digital bus, decodes the AV data therein, and displays the decoded AV data. By employing a digital bus, a source/sink system reduces or eliminates noise and other deleterious effects typically associated with analog transmission.
Use of an IEEE 1394 bus to transmit an AV stream between a source device and sink device is in its infancy and there are several drawbacks in its operation. One such drawback is the inability to properly display multiple AV streams simultaneously, known as picture-in-picture (PIP), or picture-over-picture (POP). PIP/POP functionality includes the ability to display a first selected AV stream in a larger portion of a television screen and a second selected AV stream in a smaller portion of the television screen. PIP/POP functionality allows the user to watch a primary AV stream in the full screen of the television, while monitoring a secondary AV stream in the smaller PIP/POP window, which typically overlays a portion of the full screen view.
Currently, there is no defined manner for a sink device (e.g., HDTV) receiving multiple AV streams over an IEEE 1394 bus to know that the user is requesting a PIP/POP session or that the multiple AV streams are intended for a PIP/POP session. This leaves the user with expensive state-of-the-art equipment that does not include simple PIP/POP functionality. Accordingly, there exists a need in the art for a mechanism to simultaneously display multiple AV streams transmitted over a digital link between a source device and a sink device.